Frequency multiplier circuit for electrical signaling



May 30, 1933. A. H. TAYLOR FREQUENCY MULTIPLIER CIRCUITFOR ELECTRICAL SIGNALING Filed Aug. 1925 2 Sheets-Sheet 1 HUN NOON

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FREQUENCY MULTIPLIER CIRCUIT FOR ELECTRICAL SIGNALING Filed Aug. 1925 2 Sheets-Sheet '2 W Q In \Q%QQ QQ21D m) & W

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- w im \1 v -1% L q M A, Q? N Njjmjgk sa Ma M Patented May 30, 1933 UNITED STATES PATENT OFFICE ALBERT H. TAYLOR, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR, BY MESNE ASSIGNMENTS, T0 WIRED RADIO, INC., 015 NEW YORK, N. Y., A COB?ORATION OF DELAWARE FREQUENCY MULTIPLIER CIRCUIT FOR ELECTRICAL SIGNALING Application filed August 6, 1925.

from a lower frequency piezo electric crystal controlled oscillator.

Another object of my invention is to provide an electron tube system including a piezo electric crystal controlled oscillator, a frequency multiplication circuit and an amplifier by which the multiplied frequency may be increased in amplitude and utilized for any desired purpose.

Still another object of my invention is to provide a system for multiplying the frequency of a piezo electric crystal controlled oscillator and transferring the multiplied frequency thus developed to an amplification circuit without re-action between the multiplied frequency and the frequency of the source.

A further object of my invention is to provide a frequency control circuit for a transmission system by which relatively high frequency energy may be transmitted under control of a relatively thick piezo electric crystal element whose natural frequency may be substantially lower than the transmitted frequency, thereby avoiding the grinding of piezo electric crystal elements to extremely thin plates which would normally have a natural frequency corresponding to the transmission frequency.

My invention has particular application to electron tube transmitters for radio signaling at relatively high frequency, although it will be understood that the circuit arrangement for frequency multiplication may be utilized for other purposes than radio signaling. The high frequency oscillations developed by the circuit arrangement of my invention may be utilized in carrier wave line wire communication systems or the high frequency energy may be impressed upon an antenna ground system for radiation to a dis- Serial No. 48,611.

tant station. In controlling the frequency of an electron tube oscillator the constant frequency characteristics of piezo electric crystals have been employed to maintain a master oscillator at a constant frequency. WVhere it is desired to operate at an extremely high frequency, however, the piezo electric crystals become relatively thin and fragile and it becomes impractical to control an oscillatory tube circuit at such high frequencies in this manner. In order to make use of the constant frequency characteristics of piezo electric crystals, it is desirable to operate the crystals at a relatively low frequency with respect to the frequency of the signaling energy radiated from the antenna ground system. In order to do this I have developed the frequency multiplier circuit of the present invention, which is disposed between the power amplification system and the crystal control master oscillator. Piezo electric crystals of a desired thickness producing a constant frequency may, therefore, be readily employed, the frequency multiplied and the amplitude increased, and then signaling energy impressed upon a line wire system or radiated from an antenna ground system at the multiplied frequency and maintained constant.

My invention will be lnore clearly understood by reference to the following specification and the accompanying drawings, in which;

Figure 1 illustrates a frequency multiplier system with a crystal controlled oscillator, showing a conductive system of coupling between the frequency multiplier circuit and the power amplifier circuit; and Fig. 2 shows a frequency multiplier circuit where the energy at multiplied frequency is introduced into the power amplifier circuit through a magnetically coupled system and used to excite an antenna ground circuit.

The power amplifier circuit with which the frequency multiplier circuit is associated is balanced or neutralized for the suppression of undesired oscillatory currents therein. The crystal controlled oscillator may be operated with a selected frequency to give a constant frequency output for impression upon the input circuit of the frequency multiplier. The frequency may be doubled or some other harmonic of the fundamental frequency may be produced and transferred through the coupling system through the power amplifier circuit. I have found that it is advantageous to over-excite the grid of the amplifier tube of the electron tube system with which the output circuit of the master oscillator is associated and at the same time to use an extra high negative C voltage on the grid of this tube. Thus, the combination of the high negative C voltage with powerful grid excitation causes the plate current in this second tube to assume a wave form very rich in harmonics. By properly adjusting the potential on the grid of this second tube the tube circuit develops strong harmonics which are multiples of the fundamental frequency of the master oscillator. A circuit tuned to the desired harmonic frequency, which may be considerably higher than the fundamental frequency, is provided upon which the output of the frequency multiplier circuit is impressed and from which the power for exciting the input circuit of the power amplification system is derived. The strongest excitation in the tuned circuit has been found to occur at the second harmonic, in which case the frequency multiplier tube may be considered to be a frequency doubler, although higher harmonics can be brought out and amplified and usefully employed in a signaling system.

Referring to the drawings in more detail reference character 1 designates a master oscillator tube controlled by piezo electric crystal 2 connected across the input circuit thereof in series with the crystal booster choke 3. The frequency multiplying tube or harmonic producer is indicated by reference character 4, while the power amplifier tube is shown by reference character 5. Cathodes 1a, 4a and 5a of the several tubes are energized from source 6 with radio frequency chokes 7 disposed in the supply circuit. The output circuit of the crystal controlled oscillator tube 1, includes the oscillation transformer 8 tuned by means of condenser 9 to the fundamental frequency of the crystal oscillator 2. The input circuit of the frequency multiplier tube at is connected with the oscillation transformer 8 by which the fundamental frequency of the oscillator tube 1 is impressed upon the input circuit of the frequency multiplier tube a with the output circuit of the frequency multiplier tube 4 connected to oscillation transformer 10 which is tuned by means of condenser 11 to the harmonic frequency above the frequency of the fundamental frequency developed by tube 1. The oscillation transformer 10 connects to the input circuit of the power amplifier constituted by tube 5. It will be understood that the power amplifier may comprise 2.

plurality of tubes connected one after another and that I have illustrated the power amplifier as comprising a single tube merely for the purpose of clearly explaining the invention. The output circuit of the power amplifier includes inductance system 12 which may be coupled to a line circuit or to an antenna radiating system constituted by antenna connection 14: and counter-poise 15. The plate circuits of the several tubes are 011- ergized from a high potential source 16 with radio frequency chokes 17 and 18 disposed in series therewith. The proper value of plate potential for the oscillator tube 1 is obtained by selecting the desired drop across resistance 19 by means of movable contact 20. The plate circuits of tubes 1, 4 and 5 in clude radio frequency choke coils 21, 22 and 18, respectively. The amplifier circuit is balanced or neutralized for intra-electrodc capacities by means of variable condensers 23 and 24. Plate feed condensers 25, 26 and 27 are connected in each of the tube circuits for facilitating the transfer of energy from one circuit to the other. The grid electrodes 16, 4b and 5b are each biased from the C battery 28 with radio frequency choke coils 29, 30 and 31 in circuit with the biasing tap. It will be observed that variable taps 32-, 33 and 34 are provided for selecting the C bat tery potential for the several tubes.

In order to produce the harmonic frequencies by the tube circuit a a negative C voltage higher than ordinarily used in this stage is impressed upon grid electrode 1 through connection 34 and powerful grid excitation is secured from the master oscillator, the combination of these potentials results in the forcing of the tube circuit t into oscillation with harmonics which are utilized as heretofore described.-

In Fig. 2 I have illustrated a radio trans mission system employing the frequency multiplier system, but showing the frequency multiplication circuit inductively coupled with the power amplification system. A magnetically coupled transformer system 35 hasits primary winding 36 disposed in the output circuit of the frequency multiplier tube 4. Secondary winding 37 is inductively coupled with the primary winding 36 and is tuned by means of condenser 38 to the frequency of the harmonic derived from the frequency multiplier circuit. By this arrangement, frequency considerably higher than the fundamental frequency generated in the crystal controlled oscillator circuit may be impressed upon the power amplification system.

The invention is particularly applicable to crystal controlled circuits in that a crystal of desired thickness may be employed for controlling a frequency higher than its fundamental frequency I have illustrated my invention in certain llt) CFI

preferred embodiments, but I desire that it be understood that modifications may be mad-e and that I intend no limitations upon the invention other than those intended by the scope of the appended claims.

Having thus described my invention, what I claim and desire to secure by Letters Patent of the United States is as follows:

1. A piezo electric crystal controlled si naling system comprising a relatively thibl; piezo electric crystal element having a relatively low natural frequency, an electron tube system arranged to sustain the oscillations of said piezo electric crystal element, a frequency multiplication circuit connected with said electron tube system for increasing the frequency of oscillations delivered by said electron tube system, and a separate electron tube system connected with said frequency multiplication circuit for increasing the amplitude of said oscillations at increased frequency, and means for preventing reaction between the multiplied frequency and the natural frequency of said piezo electric crystal,

In a signal transmission system, the combination of a high frequency oscillation generator, piezo electric crystal apparatus connected with said generator for controlling and stabilizing the frequency of the oscilla- "cns generated by said generator, means including a plurality of electron discharge tubes for developing oscillations bearing an harmonic relation to the frequency of the oscillations generated by said generator, said means being adapted to increase the amplitude of the harmonic oscillations, and variable means connected with the circuits of said electron discharge tubes for preventing reaction between the circuits thereof and the circuits of said oscillation generator.

8. In a signaling system the combination of an electron discharge device high frequency oscillation generator of substantially constant frequency, said electron discharge device having an electromechanical vibrator associated with its input circuit, said electromechanical vibrator having a frequency characteristic bearing a sub-harmonic relation to the signaling frequency of the signaling system, a frequency multiplying system cooperating with said oscillation generator to increase the frequency of the oscillations generated by said oscillation generator by developing harmonic frequencies of the frequency of said oscillation generator and means including an electron discharge device arrangement for increasing the amplitude of the harmonic frequency oscillations, said frequency multiplying system and said electron discharge device arrangement having means connected therewith for prevent ing high frequency currents from being impressed from the circuits thereof upon the ircuit of said or cillation generator.

4. In a high frequency signal transmission system the combination of an electron discharge device having filament, grid and plate electrodes, said electron discharge device having input and tunable output circuits connected to the electrodes thereof, a piezo electric crystal connected with the input, circuit of said electron discharge device for controlling the frequency of the oscillations generated by said electron discharge device, said output circuit being tuned to the frequency of said piezo electric element, a second electron discharge device having input and output circuits connected therewith, said second mentioned electron discharge device constituting means for generating and amplifying harmonic frequency oscillations of the electrical oscillations generated by said first mentioned electron discharge device, a tuned circuit connected into the output circuit of said second electron discharge device, said tuned circuit being resonant to the frequency of said harmonic frequency oscillations, means including connections between said last mentioned tuned circuit and another electron di charge device for further amplifying said harmonic frequency oscillations, and means connected with said tuned circuits for preventing substantial reaction between the circuits of said electron discharge devices.

5. In a high frequency transmission sys tem, a space discharge tube oscillator having input and output circuits, a piezo electric crystal connected with and adapted to control the frequency of said oscillator, an inductance and a capacity in the output circuit of said oscillator, an amplifier having a space discharge tube network including means for distorting the wave form of the oscillations generated by said oscillator whereby harmonics of said oscillations are developed in said network, at least one combination of an inductance and a capacity in said network the period of which may be selected to correspond to the period of the desired harmonic frequency oscillations, and variable means connected in said network for preventing reaction between the output and input circuits of said network and also between said amplifier and the circuits of said piezo electric crystal.

6. An oscillator and ampl fier comprising a pair of electron discharge devices provided with anode circuits tuned respectively to fundamental and harmonic frequencies and with grid circuits, means for coupling one 0 said anode circuits to one of said grid circuits, a single piezo electric element resonant to said fundamental frequency and connected in the other of said grid circuits for preventing variation in the frequencies of the currents in said tuned circuits, a source of current connected in said anode circuits, and means for preventing feed-back from the cir cuits traversed by said harmonic f 'equency to the circuits traversed by said fundamental frequency.

7. In a radio frequency transmitter, a piezo electric oscillation generator, an electronic frequency-multiplying system controlled by said oscillation generator, an electronic amplifying-system cooperating with said multiplying system to amplify the multiplied frequencies thereof and means to prevent feed-back of the multiplied frequencies toward said oscillation generator.

ALBERT H. TAYLOR. 

